ASUS ROG Ally X with RTX 4090: Real‑World Game Tests and Performance Optimization

External GPU enclosure integration delivers substantial frame rate improvements across AAA titles, pairing with the ROG Ally X

Hardware by Nakiro on Jul 14, 2025

With the advent of USB4 and compact handheld gaming PCs, external GPU setups have become more accessible than ever. A high‑end desktop GPU over a USB4 connection can transform portable hardware into a formidable gaming rig.

We explored how an eGPU can elevate the Asus ROG Ally X’s graphical prowess, the steps we took to optimise performance, and the results we achieved across a variety of benchmarks and games.

ROG Ally X, RTX 4090, Real‑World, Game Tests, Performance, Optimization, NoobFeed

Hardware Setup

The ROG Ally X features both USB4 and USB 3.2 Type-C ports, allowing you to connect an external GPU enclosure with minimal fuss. We chose the Razer Core X eGPU dock paired with an Nvidia RTX 4090, making sure to supplement its power requirements with an additional PSU to accommodate the GPU’s multiple 8‑pin connectors.

Once everything is plugged in, you simply install the latest Nvidia drivers and turn off the integrated graphics so that games launch directly on the external GPU.

Performance Optimization

To ensure conservative power limits don’t hold back the Ryzen Z1 Extreme CPU, we dove into Armoury Crate SE’s manual mode. We set a sustained TDP of 30W for the CPU, with the ability to boost to 43W for brief periods and up to 53W for 10–20 seconds.

By maximising CPU performance alongside RTX 4090, we guarantee the best possible frame rates given the constraints of a handheld form factor.

Ensuring Adequate Bandwidth

Not all USB4 docks and cables deliver the same throughput. We used the Cazy benchmark in heavy‑load mode to verify “host‑to‑device” bandwidth, aiming for values between 22 and 26 Gbit/s on a Thunderbolt 3 dock (capable of 32 Gbit/s). For PCIe diagnostics, GPU-Z confirmed an x4 3.0 link—exactly what USB4 can sustain.

If you pick up a USB4 cable online, test it first; subpar cables often max out at 18 Gbit/s, leaving performance on the table.

ROG Ally X, RTX 4090, Real‑World, Game Tests, Performance, Optimization, NoobFeed

3DMark Benchmark Results

When we ran 3DMark Night Raid with RTX 4090 connected over USB4, the total score reached 56,59. Fire Strike delivered a score of 37,200, while Time Spy landed at 19,538. By comparison, the Ally X’s integrated GPU managed just 3,518 in Night Raid, underscoring the dramatic uplift from the external RTX 4090.

Real‑World Gaming Performance

In Cyberpunk 2077 at 4K with ray tracing set to Ultra and frame generation enabled, we averaged 56 fps, with GPU usage fluctuating between 75% and 86% and power draw up to 230 W. Helldivers 2 ran remarkably well at 4K on max settings, delivering an average of 89 fps without the need for DLSS or frame generation. Overwatch 2 at 4K on Epic settings with 100% resolution scale yielded an impressive average of 162 fps.

Horizon Forbidden West, however, encountered frequent stutters at 4K on very high settings due to bandwidth limitations, a phenomenon that persisted even when dropping to low presets. GTA 5 at 4K on ultra settings held steady at around 123 fps, demonstrating solid performance despite the USB4 bottleneck.

At 4k, Shadow of the Tomb Raider on highest settings produced an average of 104 fps, though we did encounter occasional benchmark anomalies. Finally, Ghost of Tsushima at 4K on very high settings without DLSS achieved approximately 98 fps, proving that some modern titles can still run smoothly over USB4 even on demanding hardware.

Ideal GPU Pairings

Although RTX 4090 showcases the pinnacle of what eGPUs can achieve, RTX 3060 often represents a more balanced choice. It delivers excellent performance, consumes less power, and can fit into smaller enclosures that don’t require you to rig up a separate PSU.

You’ll also find all-in-one options using GPUs like Radeon 7600 MXT at attractive price points, but building a custom enclosure around an RTX 3060 remains our top recommendation for compact setups.

ROG Ally X, RTX 4090, Real‑World, Game Tests, Performance, Optimization, NoobFeed

Final Thoughts

Whether you’re aiming for ultra-high benchmarks or steady 60 fps at 4K, pairing the ROG Ally X with the right eGPU and fine-tuning power and bandwidth settings can turn a handheld into a desktop-class gaming station.

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